SolrCloud stops accepting updates

I'm attempting to import data into a SolrCloud cluster. After a certain amount of time, the cluster stops accepting updates.

I have tried numerous suggestions in IRC from Elyorag and others without resolve.

I have had this issue with 4.4, and understood there was a deadlock issue fixed in 4.5, which hasn't resolved the issue, neither have the 4.6 snapshots.

I've tried with Tomcat, various tomcat configuration changes to threading, and with Jetty. Tried with various index merging configurations as I initially thought there was a deadlock with concurrent merg scheduler, however same issue with SerialMergeScheduler.

The cluster stops accepting updates after some amount of time, this seems to vary and is inconsistent. Sometimes I manage to index 400k docs, other times ~1million . Querying the cluster continues to work. I can reproduce the issue consistently, and is currently blocking our transition to Solr.

I can provide stack traces, thread dumps, jstack dumps as required.

Here are two jstacks thus far:

http://pastebin.com/1ktjBYbf
http://pastebin.com/8JiQc3rb

I have got these jstacks from the latest 4.6 snapshot, also running solrj snapshot. The issue is also consistently reproducable with BinaryRequest writer.